Field of the Invention
The invention relates to a light guide unit and a light source module and particularly relates to a light guide unit and a light source module capable of improving non-uniform brightness.
Description of Related Art
According to the positions of the light sources, light source modules can be roughly divided into direct-lit light source modules and edge-lit light source modules. In contrast to the direct-lit light source module, the light source of the edge-lit light source module is generally disposed at a side of the light guide plate. Therefore, the edge-lit light source module is usually thinner and has broader application. For example, the edge-lit light source module can be applied to sequential naked eye stereoscopic display devices.
FIG. 1 is a schematic diagram illustrating an operating principle of naked eye stereoscopic display technology. FIG. 2 illustrates an optical simulation result of the light source module of FIG. 1. Specifically, FIG. 2 only illustrates the optical simulation result of the first light source group of FIG. 1. Referring to FIG. 1 and FIG. 2, in the edge-lit light source module applied to the sequential naked eye stereoscopic display device, the light sources can usually be divided into a first light source group LS1 and a second light source group LS2, wherein the first light source group LS1 and the second light source group LS2 are turned on alternately and coordinated with a display panel such that the right eye E1 and the left eye E2 of the user can respectively receive display images with parallax to form a stereo image in the user's head.
Generally speaking, a side surface SS of a light guide plate LGP, opposite to a light incident surface SI, usually has an arc structure AA for respectively guiding a light beam B1 from the first light source group LS1 and a light beam B2 from the second light source group LS2 to the right eye E1 and the left eye E2 of the user. As shown in FIG. 2, due to the restricted divergence angle and position of the light emitting unit (e.g. light emitting diode) in the first light source group LS1, it is difficult for a light beam B1′ to reach an area of the arc structure AA that is further away from the first light source group LS1. Moreover, a large-angle light beam B1″ exits the light guide plate LGP directly after being transmitted to a connecting surface SC of the light guide plate LGP that is near the first light source group LS1. For the above reasons, two dark areas A1 and A2 are generated at diagonal sides of the light guide plate LGP. This phenomenon causes non-uniform brightness of the display images and affects the visual effect. Thus, how to improve the non-uniform brightness of the light source module is an important issue that needs to be overcome.
P.R.C. Patent Publication No. 103329029A and U.S. Patent Publication No. 20130308185A1 respectively disclose disposing a Fresnel lens structure on the side surface of the light guide plate opposite to the light incident surface. P.R.C. Patent Publication No. 102472918A discloses an optical system that includes an additional optical element resembling the Fresnel lens structure. Taiwan Patent Publication No. 201323946A1 discloses a light guide plate having an inclined surface connected with a top surface, and a Fresnel lens structure is disposed on the inclined surface.
The information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Further, the information disclosed in the Background section does not mean that one or more problems to be resolved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art.